Miniature temperature-responsive resistor



March 27, 1956 c. c. J. ADDlNK 2,740,031

MINIATURE TEMPERATURE-RESPONSIVE RESISTOR Filed July 29, 1953 INVENTORCLAUD IUS CORN ELIUS JOHANNES United States Patent MINIATURETEMPERATURE-RESPONSIVE RESISTOR Claudius Cornelis Johannes Addink,Eindhoven, Netherlands, assignor to Hartford National Bank and TrustCompany, Hartford, Conn., as trustee Application July 29, 1953, SerialNo. 371,103 Claims priority, application Netherlands July 30, 1952Claims. (Cl. 20163) This invention relates to miniature responsiveresistors.

Miniature temperature-responsive resistors generally comprise aresistance material in the form of a sphere or droplet in which areembedded a pair of electrical conductors for elfecting external circuitconnection thereto. Suitable materials are the ceramic resistivematerials which have high negative temperature coefiicient ofresistance, e. g., the oxides of manganese, nickel, iron, cobalt, etc.Since such materials exhibit poor heat conduc tion properties, theresultant resistors sulfer from high thermal inertia, i. e., they have aslow response characteristic, and a low load capacity.

The main object of the present invention is to provide a constructionfor a temperature-responsive miniature resistor of the foregoing type inwhich the thermal inertia is minimised and the load capacity isincreased.

The invention is based on the discovery that the disadvantages inherentin the heretofore known arrangements can be materially eliminated, andsatisfactory operation assured, by efiecting the transmission of heatfrom the external environment to the portion of the resistive materialbetween the electric conductors by one of the electric conductors. Thisis accomplished, according to the invention, by providing a constructionin which one of the electric conductors is thermally connected atopposite ends to a good heat-conducting member. Moreover, the size andthe materials of the electric conductors are so chosen that most of thetransmission of heat to the portion of the resistive material betweenthe electric conductors occurs via the electric conductor connected tothe good heat-conductive member. To this end, the material of theelectric conductor connected to the good heatconductive memberpreferably has a high coefficient of thermal conductivity, and thecross-section thereof preferably exceeds that of any of the otherelectric conductors.

The invention will now be described with reference to the accompanyingdrawing in which:

Fig. 1 shows a cross-sectional view on an enlarged scale of oneembodiment of the resistance element according to the invention;

Fig. 2 is a cross-sectional view along the line II--II of Fig. 1.

The resistive device of the invention comprises a tubular holder 1 madefrom plastics, only the end of which is shown, at one end of which isprovided a metal, good, heat-conductive closing plate 2 having abevelled edge. The inner surface of the plate 2 is provided with acollar 3 enclosing a cylindrical space containing a substantially roundresistive mass 4 of temperature-sensitive or responsive ceramicmaterial. This mass is retained in place by means of a thermo-settingsynthetic resin 5, and is traversed by two electric conductors extendingin the axial direction of the holder 1. One electric conductor consistsof a platinum wire 6, for example, 100p. thick, which is bent over atboth sides of the mass 4. The upper bent portion of the platinum wire 6is soldered to the upper edge of the collar 3. This collar has alsosecured to it a temperatureconnecting wire 7 extending through theholder 1 and serving as an external connection for the conductor 6. Thelower portion of the wire 6 extends through an opening 8 of the plate 2and is soldered with its bent portion in a cavity 9 at the outer surfaceof said plate in a manner such that the outer surface of plate 2 and thebent portion of the wire 6 extend in the same plane.

The other electric conductor embedded in the resistance mass 4 consistsof a thin platinum-iridium wire 10, for example, of 25 4 diameter. Thiswire passes, parallel with the wire 6, from above and through theresistive mass and terminates at the lower outline thereof. Beyond andabove the mass 4, the wire 10 has secured to it a connecting wire 11,which, similarly to the aforesaid wire 7, extends through the holder 1.The two connecting wires 7 and 11 permit the resistance element to beconnected in a measuring circuit. The device shown is suitable formeasuring the temperature of the skin.

When bringing the aforesaid skin thermometer with the plate 2 intocontact with the skin, the temperature of which is to be measuredelectrically, exchange of heat occurs between the interior of theresistive mass 4 and the skin, the heat passing through the goodheat-conductive wire 6. Hence, the resistive mass 4 assumes veryrapidly, particularly with respect to the zone between the wire 6 andthe wire 10 which is mainly responsible for the electric resistancebetween said electric conductors, the temperature of the objectcontacting with the plate 2 and the lower bent portion of the wire 6.Alternatively, for the single thick electric conductor 6, there may besubstituted a number of wires, if desired thinner, which are jointlyconnected beyond the mass 4 to the collar 3 and the plate 2.

While I have described my invention in connection with specificembodiments and applications, other modifications thereof will bereadily apparent to those skilled in this art without departing from thespirit and scope of the invention as defined in the appended claims.

What is claimed is:

l. A miniature temperature-responsive resistor comprising a ceramictemperature-sensitive resistive material, a pair of spaced electricconductors embedded in said ceramic material, and a good heat-conductingmember, one of said conductors having opposite ends thermally connectedto said good heat-conducting member, said one conductor beingconstituted by a material and having a size at which it transmits heatto and away from the ceramic material substantially better than saidother conductor.

2. A resistor as claimed in claim 1 in which said one electric conductorconsists of a plurality of parts each of which individually traverse theresistive material.

3. A resistor as claimed in claim 1 in which the crosssection of saidone electric conductor exceeds that of the other conductor.

4. A resistor as claimed in claim 1 in which the material of said oneelectric conductor has a thermal conductivity exceeding that of thematerial of the other conductor.

5. A resistor as claimed in claim 1 in which the good heat-conductingmember comprises a flat plate having a cylindrical enclosure on one sidethereof, said ceramic material being housed in said enclosure, said oneelectric conductor being connected at one end to the end of saidenclosure remote from said plate and at its other end to the outersurface of the plate.

Grondahl Feb. 10, 1925 2,463,984

Lederer Mar. 8, 1949

1. A MINIATURE TEMPERATURE-RESPONSIVE RESISTOR COMPRISING A CERAMICTEMPERATURE-SENSITIVE RESISTIVE MATERIAL, A PAIR OF SPACED ELECTRICCONDUCTORS EMBEDDED IN SAID CERAMIC MATERIAL, AND A GOOD HEAT-CONDUCTINGMEMBER, ONE OF SAID CONDUCTORS HAVING OPPOSITE ENDS THERMALLY CONNECTEDTO SAID GOOD HEAT-CONDUCTING MEMBER, SAID ONE CONDUCTOR BEINGCONSTITUTED BY A MATERIAL AND HAVING A SIZE AT WHICH IT TRANSMITTED HEATTO AND AWAY FROM THE CERAMIC MATERIAL SUBSTANTIALLY BETTER THAN SAIDOTHER CONDUCTOR.